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Germanium Dioxide and the Antioxidant Properties of Catechols
Author(s) -
Nikolaevskaya Ele.,
Kansuzyan Artem V.,
Filonova Galina E.,
Zelenova Vera A.,
Pechennikov Valery M.,
Krylova Irina V.,
Egorov Mikhail P.,
Jouikov Viatcheslav V.,
Syroeshkin Mikhail A.
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201801259
Subject(s) - chemistry , germanium , acetonitrile , aqueous solution , molecule , dpph , reaction rate constant , medicinal chemistry , nuclear chemistry , antioxidant , inorganic chemistry , kinetics , stereochemistry , organic chemistry , physics , quantum mechanics , silicon
Complexes of tetra‐ and hexa‐coordinated germanium Adr Cat 2 Ge ( 1 , Adr Cat = adrenaline catecholate), Ald Cat 2 Ge ( 2 , Ald Cat = 4‐formylcatecholate), Ald Cat 3 Ge(Et 3 NH) 2 ( 3 ) were synthesized by the reaction of germanium dioxide with adrenaline and 3,4‐dihydroxybenzaldehyde in aqueous solution. The structures of the complexes were confirmed by 1 H and 13 C NMR and IR spectroscopy, HRMS, and elemental analysis. Cyclic voltammetry in phosphate buffer solutions (pH = 6.86) has shown the oxidation potentials E p of these complexes to be shifted by ca. 330–360 mV to more positive potentials compared to the parent aromatic diols, which means that their electron‐releasing properties were diminished by about 7.6–8.3 kcal mol –1 . A study of the kinetics of the reaction of these complexes with 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical in the presence of 5 % acetonitrile reveals a decrease of approximately one order of magnitude in the radical scavenging activity of adrenaline and model 3,4‐dihydroxybenzaldehyde upon their complexation with Ge. The corresponding rate constants drop from (3.23 ± 0.07) × 10 3 L mol – 1 s –1 (adrenaline) to (3.80 ± 0.20) × 10 2 L mol – 1 s –1 for 1 , and from (4.40 ± 0.20) × 10 3 L mol – 1 s –1 (3,4‐dihydroxybenzaldehyde) to (4.45 ± 0.25) × 10 2 L mol – 1 s –1 for 2 and 3 (germanium is equally capable to bind two or three molecules of the diol). Keeping in mind that 1,2‐diols are widespread in the living nature and often have important biological functions, these results will contribute to the understanding of role of germanium dioxide in metabolic mechanisms and to alert against unreasonable use of Ge preparations.